Variable beamwidth mechanism with first and second inflatable means for changing position of feed



Jan. 18, 1966 WHITE, JR 3,230,538

VARIABLE BEAMWIDTH MECHANISM WITH FIRST AND SECOND INFLATABLE MEANS FOR CHANGING POSITION OF FEED Filed D60. 31, 1963 3'WAY VA LVE 7 6 PRESSURE 8 SOURCE 3-WAY INVENTOR, NOEL R. WHITE,JR.

United States Patent 3,230,538 VARIABLE BEAMWIDTH MECHANISM WITH FIRST AND SECOND INFLATABLE MEANS FOR CHANGING PGSITION OF FEED Noel R. White, Jr., Phoenix, Ariz., assignor to the United States of America as represented by the Secretary of the Army Filed Dec. 31, 1963, Ser. No. 334,954 8 Claims. (Cl. 343-761) This invention relates to an antenna set, and more particularly to variable beamwidth mechanism.

In some antenna applications it is desirable to provide means for varying the beamwidth. The beamwidth of an antenna having a reflector and a feed can be varied by moving the feed oif the focus point. Prior art methods of moving the feed in reflector-feed combination-s consist of motor driven gear trains or screw mechanisms. These prior art devices are not entirely suitable when size, weight, ease of assembly, and minimum power consumption are prime considerations. Gear trains or screw mechanisms and the motors required to drive these devices add considerable bulk and weight to an antenna assembly. Also, these devices are relatively expensive and are not easily assembled or dismantled. Thus, the prior art variable beamwidth mechanisms are not very adaptable to field use, especially military field use where there is a need for ease of mobility and assembly.

My novel variable beamwidth mechanism, which utilizes inflatable means to move the feed relative to the reflector, is ideally suited for field use and other like uses. My device is small in overall size, light in weight, relatively inexpensive, and readily assembled or dismantled. Also, my variable beamwidth mechanism is easily transported because it can be packed down to a small volume.

Therefore, an object of my invention is to provide means for varying the beamwidth of a reflector-feed type antenna.

Another object of my invention is to provide a reflectorfeed type antenna having inflatable means to move the feed relative to the reflector.

Another object of my invention is to provide a variable beamwidth antenna that has light Weight easily assembled means to vary the beamwidth.

The above mentioned and other objects of my invention will become apparent from the following description and accompanying drawing in which:

The single figure shows my mechanism for varying the beamwidth of a reflector-feed type antenna.

Referring now to the drawing, the single figure shows in a reflector 1, a feed 2, two inflatable rings 3 and 4, a support 5, two flexible tubes 6 and 6 two vent tubes 8 and 8 two 3-way valves 7 and 7 and a pressure source 9.

Assume for the moment that the antenna apparatus has just been installed and that standard antenna operation is desired. Under these conditions reflector 1, which may be any standard type reflector such as a parabolic reflector, is mounted in place and support means 5, which is used to support feed 2 and inflatable rings 3 and 4, is erected at a proper distance from reflector 1. At this point rings 3 and 4 are completely collapsed. Under normal operating conditions feed 2 is placed at the focus point of the reflector. In my apparatus feed 2 is placed at the focus of reflector 1 by inflating ring 3 while ring 4 remains collapsed. This is accomplished by opening 3-way valve 7. Valve 7, by means of flexible hose 6, connects ring 3 to pressure source 9. Pressure source 9 may be any suitable type pressure source such as an air compressor or more preferably a tank containing air under pressure. When ring 3 is fully inflated, feed 2 Patented Jan. 18, 1966 is located at the focus point of reflector 1 and the aptenna is ready to be operated.

For any of several reasons it may be desirable to change the beamwidth of the antenna. This can be accomplished by defocusing feed 2. Feed 2 is defocused (moved closer to reflector 1) by inflating ring 4. Ring 4 is inflated by turning on 3-way valve 7 Valve 7 by means of flexible hose 6 connects pressure source 9 to ring 4. The amount that feed 2 is defocused depends upon the degree of inflation of ring 4. Thus, feed 2 can be defocused any amount up to the maximum degree of inflation of ring 4.

The antenna is restored to normal operating conditions by venting ring 4. Ring 4 is vented by turning valve 7 to the position that connects tube 8 to ring 4, however some additional means must be provided to completely collapse ring 4.

Various different methods may be utilized to assure complete collapse of ring 4. For example, spring devices, rubber bands of other elastic devices, mounted in such a manner as to exert pressure on ring 4, may be used. In one specific instance where my apparatus was utilized, no additional means were needed to collapse ring 4 because the reflector and feed mechanism were mounted inside a pressurized radome. The pressure inside the radome was high enough to assure complete collapse of ring 4. Thus, any device that will serve the purpose may be used to assure the complete collapse of ring 4.

If for some reason or the other it becomes necessary to move the antenna from its present site to a new location, the dismantling of the variable beamwidth apparatus is readily accomplished. Rings 3 and 4 are completely collapsed through their respective vent tubes 8 and 8 The entire apparatus can then be packed down to a small volume and easily transported to the new location.

The single figure shows my invention in its broadest form. Many variations will be apparent to those skilled in the art. For example, since ring 3 is used only to place the feed at the focal point, and therefore, remains inflated, valve 7 and tube 6 could be eliminated. In place of this apparatus ring 3 could 'be fitted with a valve and compressed air bottle arrangement similar to the valve and air arrangement used on life rafts or the like. Another factor that should be pointed out is that my invention is particularly suited for use with inflatable antenna sets because the pressure source to inflate the entire antenna can also be used for the rings. Thus, the specific embodiment shown in the drawing is to be considered only as an illustration of my invention and not as a limitation on the scope of the invention.

I claim:

1. Apparatus for varying the beamwidth of an antenna comprising: first inflatable means for placing the antenna feed at a given position; second inflatable means for moving the antenna feed from said given position; and means for inflating both said first and second inflatable means.

2. Apparatus for varying the beamwidth of a reflectorfeed type antenna comprising: first inflatable means for positioning the feed at the focus point of the reflector; second inflatable means for defocusing the feed; and means for inflating said first and second inflatable means.

3. Apparatus for varying the beamwidth of a reflector-feed type antenna comprising: a first inflatable ring for positioning the feed at the focus point of the antenna; a second inflatable ring attached to said first ring; means connected to said first ring for inflating said first ring; and means attached to said second ring for defocusing said feed.

4. A variable beamwidth antenna comprising: a reflector; a first inflatable ring; a feed attached to said first ring; a second inflatable ring attached to said first ring; and means for inflating said first and second rings.

5. A variable bcamwidth antenna comprising: a reflector; a first inflatable ring; a feed attached to said first ring; a second inflatable ring attached to said first ring; means to support said feed and said first and second rings in such a manner that said feed is located at the focus point of said reflector when said first ring is inflated; and means for inflating said first and second rings.

6. A variable beamwidth antenna comprising: a reflector; a first inflatable ring; a radio frequency feed attached to said first ring; a second inflatable ring attached to said first ring; means for supporting said feed and said first and second rings in such a manner that said feed is located at the focus point of said reflect-or when said first ring is fully inflated; first means including a first three-Way valve coupled to said first ring for inflating said first ring; second means including a second three-way valve coupled to said second ring for inflating and venting said second ring; and a pressure source coupled to said first and second inflating means.

7. A variable beamwidth antenna comprising: a parabolic reflector; a feed mechanism normally located at the focus point of said reflector; a first inflatable ring attached to said feed in such a manner that said feed is held at said focus point when said first ring is fully inflated; a second inflatable ring attached to said first ring in such a manner that said feed is defocused when said second ring is inflated; and means for inflating said first and second rings.

8. A variable beamwidth antenna comprising: a reflector; a first inflatable ring; a radio frequency feed mechanism attached to said first ring; a second inflatable ring attached to said first ring; means to support said first and second rings in such a manner that said feed is located at the focus point of said reflector when said first ring is inflated and is located closer to said reflector when said first and second rings are both inflated; a first three-way valve; a first flexible hose having one end connected to said first ring and the other end connected to said first valve; a second three-Way valve: a second flexible hose having one end connected to said second ring and the other end connected to said second valve; and a pressure source connected to said first and second valves.

References Cited by the Examiner UNITED STATES PATENTS 2,814,038 11/1957 Miller 343757 3,001,196 9/1961 Mcllroy et al 3439l5 3,039,096 6/ 1962 Ten Bosch et al 343-761 FOREIGN PATENTS 1,096,773 2/1955 France.

HERMAN KARL SAALBACH, Primary Examiner.

R. F. HUNT, Assistant Examiner. 

1. APPARATUS FOR VARYING THE BEAMWIDTH OF AN ANTENNA COMPRISING: FIRST INFLATABLE MEANS FOR PLACING THE ANTENNA FEED AT A GIVEN POSITION; SECOND INFLATABLE MEANS FOR MOVING THE ANTENNA FEED FROM SAID GIVEN POSITION; AND MEANS FOR INFLATING BOTH SAID FIRST AND SECOND INFLATABLE MEANS. 